Click "Start" to start the game - you will see a grid of 4 rows and 5 columns, you need to pick a stone from the bottom row.
Another major bonus feature and main attraction of the game is the Gladiator Bonus Bonus feature, which is triggered when you get 3 Gladiator Helmet Wild Symbols on Reels 2, 3 and 4. You can trigger this feature bonus during the base game and stadium.